[Users] SIP clients and DNS SRV

[Zen Kato]

Hi,

If we set 'Use DNS SRV: Yes' and 5 minutes REGISTRATION interval
on BT101(1.0.7.11) and GXP2000(1.0.1.9),these UACs can successfully
Re-REGISTER and INVITE other UACs on time period B, which comes 
after ser1 stops, every UACs changed their target from first 
DNS SRV(sip1) to second DNS SRV(sip2). But during time period A
if caller is not Re-REGISTERed on sip2, when he dials some number, 
there is 'no tone(white tone?)' this means the server is down. 
If the caller's phone is Re-REGISTERed on sip2 and callee's
is not yet Re-REGISTERed on sip2 in the time period A, the caller's
phone displays "404 not found". So, this is first 5 minutes out of
service probabilty time. 

After the operator of servers room knew that sip1 went down and
sip2 is take care of sip calls, he tries to repair sip1 and
restarts 'ser(openser)' on sip1. But all INVITEs are handled on 
sip2 now. BT101s and GXP2000s never automatically go back to sip1. 
So, the operator must stop sip2 untill all REGISTERs move from 
sip2 to sip1.
This is the second 5 minutes out of service probability time.    

So, (5+5)minutes out of service probability time exist.
If we set 60 minutes(default) for REGISTRATION interval,
and all Re-REGISTERs happen on 50 minutes after sip1 down,
(50+50)minutes out of service probabilty becomes high.

stop ser1                stop ser2
    |                       |
    V                       V
....|<-- 5 min-->|<--sip2-->|<-- 5min -->|<--sip1--.....->
    |service stop|service   |service stop|service 
    |            |continue  |            |continue
time|<----A----->|<---B---->|<----C----->|<----D---.....->

Do we need another backup method like Linux-HA if UACs(ONE
outgoing line only devices) don't support DNS SRV?

Regards,

Zen

------------ quote from Daniel's question -----------
Daniel-Constantin Mierla daniel at voice-system.ro
Wed Oct 26 16:46:32 CEST 2005

I do not get the question regarding the out of service interval when the 
client does not support srv. How you computed the 5+5 interval?
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